Ask the Doctors

Dear Doctor: I read that not getting enough sleep can increase my risk of Alzheimer's disease. I've had occasional trouble sleeping most of my life, and it seems to be getting worse as I get older. How worried should I be?

Dear Reader: Just like food, water and the air we breathe, getting enough high-quality sleep is vital to our well-being. As anyone who has pulled an all-nighter can attest, lack of sleep can impair reasoning and problem-solving, interfere with learning, and even lead to accidents or injury. Chronic sleep deficit, meanwhile, has been linked to health issues as serious as diabetes, obesity, cancer and heart disease.

Ongoing research continues to find a correlation between sleep deficit and various types of dementia, including Alzheimer's disease. In one of the more recent studies, participants who reported sleep problems like insomnia, poor sleep quality and daytime sleepiness had a measurable increase in amyloid plaques in their spinal fluid. These sticky proteins are considered to be indicators of Alzheimer's disease.

Just how does the sleep-wake cycle affect these Alzheimer's markers? Researchers at the University of Rochester Medical Center believe they have discovered a significant piece of the puzzle. In studies published in 2012 and 2013, they revealed the existence of a cleansing system in the brains of mice, which removes waste products at a rapid pace.

They dubbed it the "glymphatic system" because it mirrors the waste-clearing function of the body's lymphatic system, but is managed by the glial cells in the brain. Unlike cerebrospinal fluid, which plays a crucial role by circulating nutrients to the brain and clearing away debris, the glymphatic system is not passive. It's swift, efficient and reaches all corners of the brain.

What's particularly intriguing is that the glymphatic system is active during deep sleep. Researchers found that during these stages of sleep, the cellular structure of the brain shifts. The spaces between the cells open, allowing the toxins that built up while we were awake to be quickly removed. The glial cells control the flow by shrinking during deep sleep to allow for rapid movement, then swelling again during REM sleep and at waking, all but shutting the system down.

The takeaway is that a good night's sleep, which includes adequate deep sleep, literally clears out the brain. When we skimp or get poor-quality sleep that doesn't include adequate deep sleep stages, we impair the brain's ability to cleanse itself of potentially damaging waste materials.

Thus far, the glymphatic system has been confirmed only in mice. However, the mouse brain is surprisingly similar to the human brain, which is why it is used for study. As scientists build on this research, further discoveries will be made. But at the very least, we are reminded how important sleep is to good health and well-being.

As for your question about whether you should worry, we want to reassure you. Just because a symptom and a disease can be connected, it doesn't mean that they must be. The nature of research like this is to identify patterns for future study. The fact that you have experienced sleep problems does not mean that an Alzheimer's diagnosis is inevitable.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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